Process of producing salts of hydrosulfurous acid.



No. 77?,669. PATBNTED DEC. 20, 1904. A. FRANK.

PROGESS 0F PRODUCING SALTS 0F HYDROSULFUEOUS ACID.

APPLICIATION FILED MAR. a, 1900.

5m MODEL.

Wit 25,5039 v fie v a m, Z07" ller' .35 0: .121. f2. W

, I wa n UNITED STATES Patented December 20, 190%.

PATENT OFFICE.

ALBERT FRANK, OF CHARLOTTENBURG, GERMANY.

SPECIFICATION forming part of Letters Patent No. 777,669, dated December20, 1904.

Application filed March 8,1900. Serial No. 7,879,

To all, whom, it may concern.-

Be it known that I, ALBERT FRANK, a sub ject of the King of Prussia,German Emperor, and a resident of 26 Berlinerstrasse, Charlottenburg,near Berlin, in the Kingdom of Prussia, German Empire, have invented anew and useful Process of Producing Salts of Hydrosuli'urous Acid, ofwhich the following is an exact specification.

The present invention relates to an improved process for producingcompounds of hydrosulfurous acid by electrolysis according to thefollowing equation:

Already Schonbein has "found that this acid generally results from theelectrolysis of acid sulfite of sodium (Journal of Practical Chemistry,61, 193) and Groult (Com/pt. Renal, 1877, 85, 225) has found the same.Recently Villon (Lima 1 cm .Electriguc, 1890, 30, 231, and 1891, 1 1,131) and Ekker (Rec. Tree. Obi 1a., 1895) have published articles aboutthe method which, in improved form, is the subject-matter of myinvention. In spite of all care taken, for instance, by Villon highoutputs of salt with respect to the quantity of current employed nevercould be attained,

the produced hydrosulfurous acid being easily decomposed again by thefurther influence of the current or oxidized by the action of theatmospheric air. In order to avoid this decomposition or oxidation ofthe produced hydrosuliurous acid, I provide my new process, which isbased upon the fact that a secondary decomposition of this acid is notto be feared in case as initial product for all compounds of thehydrosulfurous acid salts are produced which are insoluble and depositduring the electrolysis, so that they can easily be removed from theinfluence of the current.

My process consists in producing the hydrosulfites of alkaline-earthinetals or earth metals by electrolyzing a practically neutral solutionof the bisulfite of the respective metal within a casing provided with adiapl'iragm in such manner that the bisullite solution is contained inthe receptacle in which the negative electrode is situated, while thepositive electrode is situated in diluted sulfuric acid, alkali lye, or

a suitable salt solution--as, for instance, a solution of caustic soda.During the electrolysis, as above described, the hydrosulfite of theearth mctalas, for instance, in case of a practically neutral solutionof calcium bisullite (OtLEiaSzOe) being used the hydrosullite of calcium(CaSeOi) deposits at the cathode in form of a heavy soluble crystallinemass. The reation going on during the electrolysis is the following:

CitHaS20t-l- 2 H I (JELSeOr-l- After the electrolysis is completed onlya very small quantity of hydrosulfite of calcium remains in thesolution. The hydrosullite of calcium deposited at the bottom of thereceptacle in which the cathode is situated will not be submitted to asecondary decomposition, as it is no more influenced by the current anddoes not come in contact with the atmospheric air on account of it beingcovered by a liquid. The output of salt with respect to the quantity ofcurrent is the greater the less acid is contained in the cathode liquidduring the electrolysis, and it has proved advantageous to employ ascathode lye asolution of bisuliite of calcium, which, if possible, doesnot contain more sulfurous acid than corresponds to the formula:GflSOs'l-I'IeSOa.

Equally high outputs are obtained when alkali lye or a solution of sucha salt is used as trolysis secretes an alkaline ion, so that the liquidwithin the cathode-casing remains as other. The cells C are hermeticallyclosed by rubber plugs, through which the conductors F project.

The cathode-cells C are connected to each other by means of tubes G,which pass through the rubber plugs serving for closing. these cells.These tubes G serve the purpose of leading the lye from one cell intothe following one. The first cell is connected to the storage vessel Aby means of the tube H, and the last cell 0 is connected again by meansof the tube J to the storage vessel A, so that the lye flows from thestorage vessel through the tube H into the first cell, passes throughall the cells, and is led from the last cell C through the tube J backto the storage vessel A. The flow of the electrolyte .in the abovemanner may be effected by arranging in the receptacle A an ordinarypump-piston P, provided with a valve R, this valve allowing theelectrolyte to flow through the same in the downward, but not in theupward direction. By pressing the piston P downward the electrolyteflows through the tube H, the cells, and the tube I back into thestorage vessel A into the space above the piston P. If the pistonarrives at the bottom of the storage vessel, it is moved upward, so thatthe liquid passes through the valve R. If the piston arrives at theupper end of the storage vessel, the liquid is situated underneath thesame and can be pressed again through the apparatus by moving the pistonP downward. It will be understood that any other convenient means foreffecting a flow of the electrolyte through the apparatus may beprovided. There are, further, tubes K between the different cells C,through which inert gases, as hydrogen or the like, are led through thedifferent cells of the apparatus. The cells C may be provided withliquid-gages L.

Having thus fully described the nature of this invention, what I desireto secure by Letters Patent of the United States is 1. A process forproducing hydrosulfites of the alkali-earth metals or earth metals,consisting in bringing a practically neutral solution of bisulfite ofthe respective metal into the cathode-compartment of an electrolyzingapparatus and electrolyzing the solution under such conditions that thebisulfite solution is kept practically neutral, substantially asdescribed and for the purpose set forth.

2. A process for producing hydrosulfites of the alkali-earth metals orearth metals, consisting in bringing a practically neutral solution ofbisulfite oi" the respective metal into the cathode-compartment of anelectrolyzing apparatus the anode-compartment of which contains asolution of a compound of an alkali metal and electrolyzing thesolution, substantially as described and for the purpose set forth.

In witness whereof I have hereunto set my hand in presence of twowitnesses.

ALBERT FRANK.

Witnesses HENRY HASPER, WOLDEMAR HAUPT.

